Introduce a mechanism (via the private and undocumented `ISSUE_WARNING`
option to the `cmake_policy` command) to allow built-in modules to issue
policy warnings. Update modules to use this.
This allows modules to issue policy warnings with the `CMD_POLICY`
diagnostic type, which is consistent with internally issued diagnostics.
This also tends to simplify the logic for issuing such warnings in much
the way the helpers introduced in the previous commit did for the C++
code.
Previously, `CMAKE_<LANG>_LINK_FLAGS` was an undocumented variable used
for linking executables only. Re-spell that variable mirroring the
existing spellings for shared and module libraries, and add policy
CMP0210 to preserve compatibility.
Then, repurpose `CMAKE_<LANG>_LINK_FLAGS` to provide a variable to be
used for per-language link flags for all target types, along with a
per-configuration variant. These are added to the `<LINK_FLAGS>` rule
placeholder in the generators.
Fixes: #21934
Relates: #25620
Co-authored-by: Brad King <brad.king@kitware.com>
Previously we used separate placeholders for builtin linker flags:
* CMAKE_<LANG>_LINK_FLAGS for EXECUTABLEs
* CMAKE_SHARED_LIBRARY_CREATE_<LANG>_FLAGS for SHARED libraries
* CMAKE_SHARED_MODULE_CREATE_<LANG>_FLAGS for MODULE libraries
These are now always replaced by the empty string, so drop them
from our rule variables.
Setting the `armlink --list` option without other diagnostic flags is
misleading because it produces an empty file and prevents the user from
printing diagnostics to the standard output or redirecting them to
another file.
It's unclear why the flag was added when support for ARMClang was first
added by commit 7b0abaac31 (ARMClang: Add support for Clang-based ARM
compiler, 2019-05-13, v3.15.0-rc1~111^2).
Fixes: #21538
Given the compiler to use, `CMakeFindBinUtils.cmake` automatically
determines a number of tools including linker (CMAKE_LINKER) and archiver
(CMAKE_AR) and stores them in a generated file `CMakeCCompiler.cmake` as
non-CACHE entries. The compiler-specific ARMClang.cmake then tries to
override CMAKE_LINKER and CMAKE_AR as CACHE entries.
Following the introduction of CMP0126, which is set to NEW in the test
for a working compiler, setting a CACHE entry does not replace a normal
entry of the same name anymore, resulting in a failed test due to wrong
linker and archiver.
To fix this, set CMAKE_LINKER and CMAKE_AR for ARMClang directly in
`CMakeFindBinUtils.cmake` as is done for other compilers. Check
for them in `ARMClang.cmake` to safeguard cases when a project explicitly
includes `ARMClang.cmake` prior to compiler determination (which some
projects do to work around other problems in older CMake versions).
The compile options `--march=<arch>` and `--mcpu=<cpu>` and the
link option `--cpu=<cpu>` are automatically added by CMake based
on `CMAKE_SYSTEM_PROCESSOR` or `CMAKE_SYSTEM_ARCH`. But this is not
sufficient, because armclang also supports enabling or disabling
features using `+<feature>`:
-mcpu=<name>[+[no]<feature>+...]
For example:
-mcpu=cortex-a57+nocrypto+nofp+nosimd+crc
(Reference: https://developer.arm.com/documentation/dui0774/k/Compiler-Command-line-Options/-mcpu?lang=en)
The problem is, even if a project adds a flag with features it needs,
CMake still adds flags, resulting in code that is compiled with wrong
CPU features and unable to run.
Add policy `CMP0123` to not automatically add compile or link options,
and let projects set them instead.
Co-Author: Brad King <brad.king@kitware.com>
Fixes: #21173
allows cmake to fall back to CMAKE_SYSTEM_ARCH in case CMAKE_SYSTEM_PROCESSOR is not in armclang -mcpu=list
additionally checks if CMAKE_SYSTEM_PROCESSOR belongs to armlink --cpu=list
Fixes: #19962
Matthew Woehlke
scivision
Tyler YankeeandBrad King
Daniel Brondani
Lingkai Dong
Marc Chevrier
Jean-Christophe Fillion-Robin
Osama Moharam
Ben Boeckel
Johan Stridkvist